Reducing semiconductor device feature geometries plays a vital role in reducing the size and increasing the speed of integrated circuits. Therefore, the techniques used to achieve these smaller device feature geometries are continually evolving. Photolithography is one such evolving technique. In a conventional photolithographic process, a photosensitive film, such as a photoresist, is formed on a surface of a substrate. The photoresist is exposed to a source of radiation through an imaging device (i.e., a mask, reticle) to form a pattern thereon. Exposed regions of the photoresist undergo a transformation, whereby subsequent development forms a topographic pattern in the photoresist; some regions of the photoresist remain and some are removed. In areas where the photoresist has been removed, additional processing may transfer the pattern to the substrate surface. Conversely, in areas where the photoresist remains, the photoresist serves to protect the underlying substrate during the additional processing.
Advances in photolithography have lead to the development of high resolution, deep ultraviolet (100 nm-300 nm) or extreme ultraviolet positive-tone and negative-tone photoresists that may be used to pattern images with less than quarter micron geometries. However, the use of deep ultraviolet wavelengths of radiation during the photolithographic process may cause increased reflection from the surface of the underlying substrate. Reflected radiation may in turn cause major problems, such as thin film interference effects and reflective notching. Several techniques have been developed to mitigate the back reflection of the radiation used to activate the photoresist. One such technique is the use of a bottom antireflective coating (BARC). A BARC is a radiation-absorbing layer that is interposed between the photoresist and the substrate surface. BARCs may be composed of either organic or inorganic materials. Although BARCs may reduce the amount of reflected radiation, the use of BARCs in the photolithographic process adds additional acts to the photolithography process, such as additional deposition and etching acts. While etching may effectively remove the BARC, the etching conditions may also detrimentally affect at least one of the overlying photoresist and the substrate surface. For example, the etching may cause variances in critical dimensions due to the fact that the photoresist is not entirely resistant to the etching conditions.
One proposed solution to the BARC removal problem has been the use of developable bottom antireflective coatings (dBARCS). The difference between a dBARC and a BARC is that the dBARC may become soluble in a developer and, therefore, may be removed during the photoresist development. The use of a dBARC may reduce the total number of process acts while avoiding the damage caused by etching. One problem with conventional dBARC technology is the use of plasma etching in the subsequent patterning of the substrate material below the patterned dBARC. During this plasma etching, the dBARC effectively serves as a mask to enable the selective removal of portions of the substrate material. However, plasma etching of the substrate material may overetch or imprecisely etch the sidewalls of the patterns (e.g., openings) formed in the dBARC. In addition, excess sidewall removal of the dBARC material results in the loss of critical dimensions of patterned dBARC features, which may, in turn, cause the loss of critical dimensions of patterned resist features and of features formed in the substrate material.
In view of this problem, there remains a need for forming and patterning a developable antireflective material, such as one that exhibits enhanced etch resistance over conventional developable bottom antireflective coatings.